The invention relates to safety belt retractors for use in vehicles, such as automobiles, to restrain an occupant, either a passenger or a driver, in his seat during emergency conditions. More particularly, the invention relates to safety belt retractors which are belt sensitive, that is, sensitive to certain movements of the safety belt. The invention may also be used in retractors which are dual sensitive, that is, sensitive to certain movements of the vehicle and sensitive to certain movements of the safety belt. Still more particularly, the invention relates to improvements in a flywheel and clutch mechanism of a retractor, such as the retractor disclosed and claimed in U.S. Pat. No. 3,918,658, filed in the name of H. Beller on June 15, 1973, entitled "Seat Belt Retractor Having Inertial Device Activated By Two Stimuli". The improvements of the present invention allow the use of less expensive polymeric parts used in the flywheel and clutch mechanism of the retractor, as compared to the number of parts used in previous retractors, such as the retractor of U.S. Pat. No. 3,918,658. The improvements of the present invention also reduce the amount of wear on a pawl used with a pendulum mechanism of a retractor, such as the retractor of U.S. Pat. No. 3,918,658. These improvements are significant because they simplify the manufacture and operation of the retractor and reduce the cost of the retractor.
Some prior art safety belt retractors include a vehicle sensitive mechanism, such as a pendulum mechanism, which locks the retractor and prevents further unwinding of the safety belt when the vehicle experiences a given magnitude of acceleration, deceleration, tipping or overturning. Such retractors are known as "vehicle sensitive retractors." Other prior art safety belt retractors include a belt sensitive mechanism, also known as a web sensitive mechanism, which locks the retractor when acceleration in withdrawal of the safety belt from the retractor exceeds a given magnitude. Still other prior art retractors include both a vehicle sensitive mechanism and a belt sensitive mechanism, such as the retractor of U.S. Pat. No. 3,918,658.
The vehicle sensitive mechanism of U.S. Pat. No. 3,918,568 includes a pendulum which causes a clutch to slip with reference to a flywheel. The belt sensitive mechanism of Pat. No. 3,918,658 uses the same clutch and flywheel. The clutch acts in conjunction with the flywheel, but the clutch acts as a separate component only for the vehicle sensitive mechanism, not for the belt sensitive mechanism. In the belt sensitive mechanism, the clutch turns with the flywheel as one unit to provide a mass and a moment of inertia which causes an actuating plate to rotate a limited distance. Prior art flywheels are usually made of die-cast metal, which is expensive to manufacture. For example, ratchet wheel 61 of U.S. Pat. No. 3,918,658 is made of a die-cast metal.